Diseases of aorta are common in the general population and may include endovascular disease, including aneurysms and aortic dissections.
Endovascular disease may be characterized by weakened vessels due to elastin breakdown, which results in dilation of vessels and aneurysm. An aneurysm is a sac formed by localized dilatation of the wall of an artery, a vein, or the heart. Common areas where aneurysms occur and cause adverse medical conditions include the coronary arteries, the carotid arteries, various cerebral arteries, and the thoracic and abdominal aorta as well as iliac and femoral arteries. When a local dilatation of a vessel occurs, irregular blood flow patterns result in the lumen of the vessel, sometimes leading to clot formation. Typically, the wall of the vessel also progressively dilates and weakens, often resulting in vessel rupture. Vessel rupture, in turn, often causes dramatic negative consequences such as a stroke, when a cerebral vessel ruptures, or even death, when an abdominal aortic aneurysm (“AAA”) ruptures. Continued degeneration can result in an increase in aneurysm size due to thinning of the medial connective tissue of the aorta and loss of elastin.
Aortic dissections occur when the inner layer of the aorta's artery wall splits open (dissects). The normal aorta contains collagen, elastin, and smooth muscle cells that contribute to the intima, media, and adventitia, which are the layers of the aorta. Hypertension with aging is believed to contribute to degenerative changes that may lead to breakdown of the collagen, elastin, and smooth muscle cells and ultimately dissection of the aorta. Aortic dissection is more likely to occur where pressure on the artery wall from blood flow is high, such as the proximal aorta or the ascending aorta (the first segment of the aorta). When the aortic wall splits, the pulses of blood can penetrate the artery wall and its inner layer, causing the aorta to tear or split further. This tear usually continues distally (away from the heart) down the descending aorta and into its major branches. Less often, the tear may run proximally (back toward the heart). Aortic dissection can also start in the descending (distal) segment of the aorta.
In light of these consequences, improved devices and methods of treating and/or preventing aneurysms and aortic dissections are constantly being sought. Although the following discussion focuses on AAA treatment and prevention, it is equally applicable to endovascular disease in other locations, and aortic dissections.
Various implantable medical devices are advantageously inserted within various portions of the body. Minimally invasive techniques and instruments for placement of intralumenal medical devices have been developed to treat and repair undesirable conditions within body vessels including treatment of conditions that affect blood flow such as abdominal aortic aneurysm. Various percutaneous methods of implanting medical devices within the body using intralumenal transcatheter delivery systems can be used to treat a variety of such conditions. One or more intralumenal medical devices, such as tubular stent grafts, can be introduced to a point of treatment within a body vessel using a delivery catheter device passed through the vasculature communicating between a remote introductory location and the implantation site, and released from the delivery catheter device at the point of treatment within the body vessel. Intralumenal medical devices can be deployed in a body vessel at a point of treatment and the delivery device subsequently withdrawn from the vessel, while the medical device is retained within the vessel to provide sustained improvement in valve function or to increase vessel patency. For example, an implanted stent graft can improve vessel function by permitting relatively less turbulent fluid flow through the stent graft conduit bridging the site of an aneurysm.